1. Technical Field
The present invention relates to a projector.
2. Related Art
As is widely known, a projector is a device that includes a light source, an optical modulation device, and a projection lens and displays an image on a screen by modulating light emitted from the light source by using the optical modulation device and projecting the modulated light onto the screen by using the projection lens. Generally, projectors include a lamp such as a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp as the light source. However, recently, in order to achieve low power consumption, miniaturization, lightness, and the like, projectors including solid-state light sources such as an LD (Laser Diode) and an LED (Light Emitting Diode) have been actively developed.
As one type of projector including a solid-state light source, there is a projector in which red light, blue light, and green light necessary for color display are acquired by exciting a fluorescent body using light (for example, blue laser beams or ultraviolet laser beams) emitted from the solid-state light source. By acquiring three types of color light (red light, blue light, and green light) necessary for color display by using only one solid-state light source, such a projector can achieve cost reduction, miniaturization, and the like, compared to a case where the projector includes a plurality of solid-state light sources.
In JP-A-2005-85871 and JP-A-2002-45329, a technology for preventing an unnecessary increase in the optical output in a device having a solid-state light source such as an LD is disclosed. To be more specific, in JP-A-2005-85871, a sensor (for example, a light-intensity sensor) that detects the operation status of a laser oscillation unit is arranged, a reference value (reference range) of a signal transmitted from the sensor corresponding to each control amount for the laser oscillation unit is stored, and the abnormality of the sensor is determined based on the signal acquired from the sensor, the stored reference value, and the like so as to stop the laser beam. In addition, in JP-A-2002-45329, the output of excitation light emitted from a semiconductor laser is detected, and the operation of the semiconductor laser is stopped in a case where the output of the excitation light is equal to or more than a set value.
As described above, since the projector needs to project light modulated by the optical modulation device onto the screen, the projector includes a solid-state light source having a high-level output. In the projector including the solid-state light source having a high-level output and the above-described fluorescent body, in a case where the fluorescent body is damaged, there is a concern that light having the high-level output that is emitted from the solid-state light source will be directly output to the outside of the projector. Accordingly, in such a projector, similarly to the devices disclosed in JP-A-2005-85871 and JP-A-2002-45329 described above, a countermeasure for preventing the light emitted from the solid-state light source from being directly output to the outside is necessary.
Here, according to the above-described technologies disclosed in JP-A-2005-85871 and JP-A-2002-45329, in a case where the optical output of the solid-state light source increases to be equal to or more than a predetermined value, abnormality is determined, and the solid-state light source is stopped or the like. Thus, in a case where the optical output of the solid-state light source is within a normal range, the determination of abnormality is not made. Accordingly, in the technologies disclosed in JP-A-2005-85871 and JP-A-2002-45329, a problem (a problem that the light having a high-level output emitted from the solid-state light source is directly output to the outside of the projector) that may occur due to damage in the above-described fluorescent body cannot be prevented.
In addition, in a case where the fluorescent body is degraded, the balance of three types of light (the red light, the blue light, and the green light) that are necessary for color display may collapse, so that the color of an image displayed on the screen changes from the original color. Furthermore, since the degradation of the fluorescent body is promoted in accordance with a rise in the temperature, in a case where the solid-state light source is driven without the degradation of the fluorescent body being considered at all regardless of the actual occurrence of the degradation of the fluorescent body, the lifetime of the fluorescent body may be much shortened. Accordingly, in the projector including a fluorescent body, in order to prevent the occurrence of a color change and to lengthen the lifetime, it is important to check the degraded status of the fluorescent body.